Air heating apparatus



July 4, 1964 1.. BLOCK ETAL AIR HEATING APPARATUS Filed July 11, 1960 INVENTOR.

ATTORNEY.

United States Patent 3,140,706 AIR HEATING APPARATUS Leo Block, Monterey Park, and John H. Hollingsworth,

Fullerton, Califi, assignors to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed July 11, 1960, Ser. No. 41,982 2 Claims. (Cl. 126110) This invention relates broadly to air heating apparatus. More particularly, this invention relates to apparatus of the type utilized to heat air for transmission to or within an enclosure for the purpose of supplying and maintaining air within the enclosure at a temperature sufficient to assure comfort to the occupants of the enclosure.

Equipment of the type to which this invention pertains includes a heat transfer unit composed of a material having a relatively high heat transfer coefficient and formed to accommodate the flow of a gaseous combustible mixture subject to suitable ignition during its passage through the unit, a fan assembly for directing air over the surface of the heat transfer unit for the purpose of heating the air, and a housing having suitable inlets and an outlet for confining the air flow under the influence of the fan. Conventional air heating units or furnaces, as they are more commonly known, are constructed in relatively large, bulky casings made necessary by the design concepts currently employed in the manufacture and assembly of the units. With the emphasis on effective utilization of space in the design and construction of residential units, a definite need exists for a forced air furnace of the kind under consideration that is more economical to construct and which may be incorporated within a housing or casing of relatively small dimensions without the sacrifice of capacity or efiiciency.

A particular type of air heating apparatus having the construction described is known as a horizontal flow fur nace. are arranged so that flow of the air to be heated occurs through the unit in a substantially horizontal path. This particular unit is advantageously employed in residential units provided with a limited attic area commonly called a crawl space. Suitable ductwork is connected to the outlet of the furnace to deliver air heated in the furnace to the various rooms within the enclosure. Ductwork is also provided for the purpose of supplying air, commonly called return air, to the unit from the rooms.

In view of the limited space within which the horizontal air furnace is located and the difiiculty in gaining access to the space, it is often difiicult to service the furnace. Accordingly, it is one of the objects of this invention to provide a horizontal air furnace that may readily lend itself to different attic arrangements and thus be capable of installation in crawlspaces in order to accomplish servicing of the unit.

The heating capacity of air heating units of the kind described is determined, in part, by the temperature to which the material employed in the heat transfer unit may be subjected together with the manner in which air to be heated is introduced over the heat transfer unit. Another object of this invention is the provision of a novel fan-heat transfer unit construction which provides an improved heat exchange between the relatively high temperature ignited gas-air stream flowing within the heat transfer unit and the air forced over the outer surface of the heat transfer unit.

A still further object of the invention is the provision of an improved air heating apparatus employing a novel fan-heat transfer unit sub-assembly, wherein said subassembly may be effectively utilized with a burner construction, employed for the purpose of supplying the com- The housing and the elements assembled therein bustible air-gas mixture and the necessary ignition, of relatively simple and inexpensive construction.

A further object of the invention is the provision of a novel fan-heat transfer unit sub-assembly for use in a furnace or air heating apparatus of the type under consideration wherein novel design concepts are employed for the purpose of achieving substantially lower manufacturing costs, and capacity and efficiencies heretofore attainable only with units involving substantially greater heat transfer surface area.

Another object of this invention is the provision of an air heating apparatus arranged within a housing or casing in such a manner that servicing of the components of the apparatus may be accomplished regardless of the orientation of the apparatus upon installation with removal of only one panel on the housing.

A further object of the invention is the provision of an improved air heating apparatus of the type under consideration wherein the components of the apparatus are so constructed that they may be readily assembled within a housing or casing capable of satisfying a variety of installation requirements to thereby provide apparatus having substantial installation design flexibility.

In attaining the objects of this invention there is pro vided an air heating apparatus comprising a heat transfer unit having a first section and a second section disposed substantially normal to the first section providing a confined path for the flow of a medium having a relatively high temperature, a fan for supplying air over the surface of the heat transfer unit, a housing for said fan having a portion supporting one end of the heat transfer unit so as to substantially enclose the first portion of the heat transfer unit, and means cooperating with said housing to enclose a substantial part of the second portion of the heat transfer unit.

These and other objects of the invention will be apparent from a consideration of the ensuing specification and drawings in which:

FIGURE 1 is a perspective view of an air heating apparatus constructed in accordance with the invention;

FIGURE 2 is a view, partly in elevation, partly in section of the apparatus shown in FIGURE 1; and

FIGURE 3 is a perspective view of a heat transfer unit employed in the apparatus.

In order to more readily appreciate the invention, it will be described as it applies to a conventional horizontal flow furnace utilizing a gaseous mixture as the fuel supplied to the heat exchanger. It will be understood that the invention may be employed in other forms of air heating apparatus that may in turn utilize other forms of fuel. In the usual type of horizontal flow forced air furnaces two separate sections are provided for assembly into a common housing having a generally rectangular parallelepiped configuration. The first section includes a centrifugal blower wheel and its conventional housing commonly referred to as a scroll employed for the purpose of directing air from the wheel through a portion thereof of a gradually increasing cross-section to convert the velocity of the air stream to pressure so as to increase the static pressure and reduce the velocity of the air discharged from the blower. The second section accommodates the heat exchanger and is assembled adjacent to the first section so as to receive the air, discharged by the blower, over the surface of the heat exchanger. After traversing the surface of the heat exchanger the air exits the furnace through a duct connected in a system having outlets at locations remote from the furnace. In the construction described, burner means are provided for supplying an ignited combustible fuel in the heat exchanger. The products of combustion are collected in a header at the end of the heat exchanger remote from the portion accommodating the burner assembly and are vented to the atmosphere through a fixed opening determined by the design of the heat exchanger. In the conventional unit, the heat exchanger consists of a lower header, an upper header connected to the lower header by one or more tubular members. The burner assembly is inserted in the lower header and projects a pattern of flame upwardly through the tubular member or members. The bottom portion of the lower header of the heat exchanger is relatively inefficient as a heat transfer surface. Effective heat transfer occurs up the tube surface from the burner.

In the construction to be described herein, it will be evident that the heat transfer unit or heat exchanger is so constructed and arranged with regard to the fan assembly that substantially the entire surface of the heat transfer unit contributes to the heat transfer action and does so under circumstances such that the losses inherent in the fan operation are utilized to enhance the heat transfer action. This is accomplished primarily by forming the heat transfer unit into a configuration including a first substantially horizontal section, as indicated above, through which the flame from the burner is directed and a substantially vertical section at one end thereof. With this construction the heat transfer unit may be inserted into the housing of the fan through the discharge end thereof and positioned so that a considerable portion of the unit may be disposed adjacent to the blower Wheel and receive air immediately upon its discharge from the wheel. In order that eflicient fan operation be maintained, provision must be made to compensate for the space in the fan housing or scroll, occupied by the heat transfer unit. To this end, the conventional scroll is modified to the extent that portions thereof are displaced laterally of the centerline of the scroll. Thus the normal energy losses in the diffuser, due to eddy currents and turbulence as the air stream resists the change of direction imposed on it by the scroll surface, are used in the interests of promoting enhanced heat transfer action. The tubulence along with the vigorous intermixing of the air attendant the turbulence improves the heat exchange action in the portion of the heat transfer unit where the surface temperatures are relatively high and under circumstances where the velocity of the air is relatively high and the initial temperature of the air is lowest. Inasmuch as it is known that the rate of heat transfer in the equipment under consideration is proportional to (a) the diflerence in temperature between the heat transfer surface and the air at a given point and (b) approximately the square of the velocity of the air over the heat exchanger, it will be appreciated that a substantial efficiency gain is achieved in the construction proposed.

Referring more particularly to the drawings wherein an air heating unit incorporating the instant invention is illustrated, a base pan formed of sheet metal material includes a bottom wall 11, a front wall 12, side walls 13, and a rear wall 15. The rear wall and side walls 13 are provided with flanged portions 16 and 17. The side walls of the base pan serve to mount certain of the components of the air heating unit as will be hereinafter described.

Extending upwardly from opposite sides or corners of the base pan are corner posts 20 and 21. These posts are formed of a sheet metal material and have a generally L-shaped configuration when viewed in section; however, it will be apparent that a flange 22 is integrally formed with part of one side of the corner post. In the forward portion of the base pan, provision is made for the accom modation of the burner assembly used with the air heating apparatus. The chamber housing the burner assembly is isolated from the remainder of the unit so that the air necessary for combustion does not mix with the air stream which is being supplied to the heat exchanger. The chamber is formed with a top cover 24 which is secured to the side walls of the base pan through integrally connected opposed attachment members 25. Top cover 24 has side extensions projecting forwardly of the unit, note,

FIGURES l and 2. The attachment members 25 are provided with web portion 26 which is secured to a corner post, a top flange portion 27 which is secured to the cover 24 and extends rearwardly thereof, a bottom flange 28 which is secured to the side wall 14 of the base pan. In addition, there is a central web portion 29 extending forwardly of the air heating unit and terminating in a rearwardly extending flange, not shown.

Centrally positioned within the enclosure formed by the members 24 and 25 is a transverse plate member 32 having a series of openings 33. The function of the plate 32 is to serve as a support member for one end of the heat transfer unit or heat exchanger to be later described and to serve as a divider between the chamber housing, the burner assembly and the inside of the fan scroll. As is evident from a consideration of FIGURE 1, the burner members are so arranged within the burner assembly chamber so that the flow of fuel from the burners is directed to the heat transfer unit through openings 33 provided in the plate 32. In addition to the components described above, there are provided, overlying the top flange 27 of the attachment member 25 on the member 24, track elements 34 which are in the form of a Z when viewed in section. The function of the track elements is to slidably receive and confine a portion of the blower housing or modified scroll.

Located at the rearward end of the attachment members 25 are opposed wall members 35 having an upper portion 36, a central portion 37, and a lower portion 38 defining an opening therebetween. The central portion is inclined with respect to the substantially parallel upper and lower portions. Each member 35 is provided with flanges 39, 40 for the purpose of securing it to the base pan and providing a mounting for a plate 42 having openings 43 to which the other end of the heat transfer unit is attached. A collector shroud 45 is secured to plate 42 for the purpose of providing an enclosure for removing from the heat transfer unit the products of combustion through a conventional vent that may be connected to either side of the furnace in communication with opening 43 provided therein. The members 24 and 35 together with collector shroud 45 and that portion of the members 29 forwardly of the plate 32 form a partition defining a compartment within which the heat transfer members are disposed.

A top cover plate 46, likewise formed from sheet metal, is provided with appropriate flange portions for the purpose of connecting the top cover to the uppermost portions of the corner posts. The top cover, in addition to the connecting flange, has an extension 47 extending substantially parallel to its top portion which is arranged to act with the corner post flange 22 and the base pan side wall 16 flange and a wrapper flange to be later described to provide openings for the purpose of mounting louvers, access doors or a connecting member supplying return air to the unit.

Referring more particularly to FIGURE 2, there is provided a centrifugal blower wheel 50 together with a partial scroll 51 which is adapted to be assembled in such a manner that the flanges 52 provided at the sides of the scroll walls will slide underneath track member 34 and engage the central portion and upper portion of the partition 35. Mounted on the outer surface of the scroll through bracket is a motor for the blower wheel. With the construction described air flowing from the blower wheel in the manner indicated by the arrows in FIGURE 1 enters the compartment formed by the partition described above through the opening between the spaced members 35 and the spaced forwardly extending sides of member 24. The motor is arranged so that its power shaft is connected to and positioned within the confines of the wheel in the manner shown in FIGURE 2.

The heat transfer unit employed in the furnace serving as the subject of this invention is of a unique design and includes a first horizontal portion 53 integrally connected to a second vertical portion 54. The heat transfer unit is preferably formed of cold rolled steel and is of conventional clamshell design wherein the sides of the heat transfer unit are mounted in spaced relation to one another and seam welded about their inwardly formed peripheral portions or flanges. Conventional spacing bosses and reinforcing ribs complete the heat transfer unit. As indicated above, the heat transfer unit is secured to the plate 32 through a conventional welding operation. The other end of the heat transfer unit is secured to the vent plate 42 in a similar welding operation. The ends of the tubular members that are welded to plates 32 and 42 are preferably flared. It will be appreciated that the fan will deliver air from the blower wheel through the scroll which has been modified to the extent that additional area is employed for the purpose of compensating for the scroll area taken up by the heat exchanger which is mounted in the plate 32.

To complete the assembly of the furnace, there is provided a wrapper member 58 formed of sheet metal and which includes a top portion 59 and opposed side portions 61 having vertical ranges 62. A flange 80 defines an opening for receiving ductwork to which air from the furnace is supplied. The wrapper is secured at the lower extremities of its side portions to the side walls of the base pan. The wrapper extends over that portion of the furnace housing the vertical portion of the heat transfer unit. As is evident in FIGURE 3, the heat transfer unit consists of a series of tubular members constructed as described above and arranged to form a series of paths for the flow of the ignited mixture of gas and air fed thereto by the burners. The first portion of the path is of generally horizontal extent from which point the path curves upwardly into a substantially vertical portion. The length of the horizontal portion is traversed by the flame issuing from the burner which in the organization illustrated is a Bunsen-type atmospheric burner known as a horizontally directed inshot type burner. Thus the surface of the heat transfer unit in the area adjacent the end secured to the plate 32 is at a substantially high temperature. It will be apparent that with the heat transfer unit arranged within the area normally considered to be a portion of the conventional scroll, air flowing from the wheel is placed in immediate contact with the portion of the heat transfer unit having the highest temperature. As indicated above, the losses normally inherent in a centrifugal blower scroll are utilized for the purpose of maintaining relatively high velocity of the air over the heat transfer unit greatly enhancing the heat transfer action. As a result of the increased efficiency inherent in the fan-heat transfer unit construction described, it is possible to obtain higher air heating performance from any given material. This factor becomes important when it is realized that there are definite temperature limitations that apply to specific types of heat transfer unit material.

To illustrate this advantage the use of a heat exchanger formed of cold rolled steel is limited by the practical working temperature of the material. Thus if it is desired to design a heat transfer unit with a preselected fan, fix ing the air quantity to be delivered over the unit, the temperature of the air leaving the furnace is accordingly limited. A leaving temperature in excess of this value, with the same fan, would require a heat exchanger having its surfaces coated with porcelain enamel or of some other material such as stainless steel so that the working temperature could be elevated. With the increased heat transfer action available in the fan-heat transfer unit assembly proposed, a greater leaving air temperature may be obtained with a similar fan and cold rolled steel heat exchanger obviating the need for the protective coatings referred to above.

It has been established that although the modified scroll construction which may be described as the fan housing and opposed side walls 29 rearward of plate 32, is a departure from the conventional scroll, the power requirement for the motor controlling operation of the fan is approximately the same as the requirement for the same fan with the conventional scroll.

In the construction illustrated for the purpose of describing the invention, the housing 51 is formed from a conventional scroll modified to include the horizontal flange 52 slidably engaging the member 34 as shown in FIGURE 1. With the construction shown it will be obvious that the connection for the return air duct may be made on either side of the furnace by securing the return air duct to the flanges 16, 22, 47, 62, the particular side being dictated by convenience according to the installation involved. A louvered closure member may then be attached to the other side. Ventilation air as well as return air may then be drawn into the fan housing and discharged over the heat transfer unit in the manner described. The heated air, after passing over the heat transfer units enters the supply duct attached to wrapper flange 80 and flange 17.

As pointed out above conventional heat transfer units involve inefficiencies in that the lowermost portions are practically ineffective for the transfer of heat. With the construction proposed, the entire surface is available for heat transfer, note FIGURE 2. The novel arrangement of burner and the horizontal tubular portion of the heat transfer unit permits maximum usage of the surface. With this arrangement the energy present in the gas-air mixture ejected from the burner in combination with a portion 0 fthe energy released in the process of combustion results in a confined horizontally expanding flame front. This provides a construction which renders optimum utilization of the bottom of the heat exchanger as a heat transfer surface.

An additional feature of the invention disclosed herein is the ease in which the parts may be serviced. An imperforate closure plate, not shown, is releasably attached to the unit so as to normally prevent access to the area bounded by the top cover 46, the upper surface of member 24 and opposed side members 20 and 21 between the member 24 and top cover 46. Removal of the plate permits the fan together with its housing and motor to be slidably removed from the furnace. Likewise from the same position the burner assembly may be serviced.

The flue for disposing of the products of combustion may be attached to either side of the furnace, each of which is provided with an opening 43'. A closure plate having a configuration compatible with the shape of opening 43' is then applied to the other opening.

While we have shown a preferred embodiment of our invention, it is obvious that other embodiments will be apparent to those skilled in the art and it is, therefore, intended that the invention be limited only within the scope of the appended claims.

We claim:

1. A housing for an air heating apparatus comprising a pan having opposed side walls serving as a base support for said apparatus, said pan having side portions thereof forming horizontal flanges; upright structural members secured to opposed outer end corners of said base pan, said members having vertical flange portions, a top cover having depending sides provided with horizontal flanges extending outwardly thereof, said top cover being secured to the upper ends of said upright structural members over a portion of the base pan in spaced relation thereto, a wrapper forming housing walls having opposed side portions connected to the side walls of the other portion of said base pan to form continuations thereof and a connecting top portion serving as a continuation of said top cover, the side edge portions of said side portions being bent outwardly from the plane thereof to form vertically extending flanges adapted to form in association 51 and the area defined by the inner surfaces of plate 32 with the pan horizontal flanges, the top cover horizontal flanges and the upright structural member vertical flanges, a mounting for a return air duct or closure member.

2. Air heating apparatus comprising casing means forming an enclosure having an inlet and an outlet; heat transfer members arranged in spaced relation to one another and to said casing in said enclosure, said heat transfer members having a first substantially horizontal section, the horizontal length of which is relatively large compared to its height and a second substantially vertical section, the horizontal length of which is relatively small compared to its height; burner means for supplying an ignited fuel-air mixture to the horizontal section of each of said heat transfer members, said heat transfer members forming a path for the flow of said ignited fuel mixture having a first horizontal portion, the horizontal length of which first portion is relatively large compared to the height and width thereof and a second vertical portion the height of which second portion is relatively large relative to horizontal length while the width remains substantially constant with the width of said first portion, the horizontal length of said second portion being greater than the width thereof; plate means disposed within said enclosure supporting one end of the horizontal sections of the heat transfer members in spaced relation to said casing means, said plate means having openings therein providing inlets for said members; partition means including a substantially vertical section and a substantially horizontal section, said vertical section supporting the other end of said heat transfer members and providing outlets for said heat transfer members, said partition means forming with said casing means and said plate means a compartment within said enclosure accommodating said heat transfer members, said partition means defining an opening having a vertical portion and a horizontal portion; a fan assembly including a fan member and a partial scroll supported on said partition means and discharging through the opening in said partition means so that air discharged from the fan is initially directed downwardly over the first substantially horizontal sections of the heat transfer members and forwardly over the second substantially vertical sections of the heat transfer members utilizing the space defined by the casing, plate and partition means for diffusion to the outlet of said casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,877,905 Le Grand Sept. 20, 1932 2,270,395 Tjernlund Jan. 20, 1942 2,444,825 Higley July 6, 1948 2,453,912 Higley Nov. 16, 1948 2,564,257 Herbster Aug. 14, 1951 2,582,071 Schultz Jan. 8, 1952 2,808,047 Jaye et al. Oct. 1, 1957 2,864,359 Vaughn Dec. 16, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 3 14 .0 706 July l4 1964 Leo Block et al a It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 2 line 12, before "air" insert improved column S line 22 for "ranges" read flanges column 6 line 2O for "units" read unit Signed and sealed this 19th day of January 1965,

(SEAL) Attest:

ERNEST W. SWIDER v EDWARD J. BRENNER Attesting Officer y Commissioner of Patents 

2. AIR HEATING APPARATUS COMPRISING CASING MEANS FORMING AN ENCLOSURE HAVING AN INLET AND AN OUTLET; HEAT TRANSFER MEMBERS ARRANGED IN SPACED RELATION TO ONE ANOTHER AND TO SAID CASING IN SAID ENCLOSURE, SAID HEAT TRANSFER MEMBERS HAVING A FIRST SUBSTANTIALLY HORIZONTAL SECTION, THE HORIZONTAL LENGTH OF WHICH IS RELATIVELY LARGE COMPARED TO ITS HEIGHT AND A SECOND SUBSTANTIALLY VERTICAL SECTION, THE HORIZONTAL LENGTH OF WHICH IS RELATIVELY SMALL COMPARED TO ITS HEIGHT; BURNER MEANS FOR SUPPLYING AN IGNITED FUEL-AIR MIXTURE TO THE HORIZONTAL SECTION OF EACH OF SAID HEAT TRANSFER MEMBERS, SAID HEAT TRANSFER MEMBERS FORMING A PATH FOR THE FLOW OF SAID IGNITED FUEL MIXTURE HAVING A FIRST HORIZONTAL PORTION, THE HORIZONTAL LENGTH OF WHICH FIRST PORTION IS RELATIVELY LARGE COMPARED TO THE HEIGHT AND WIDTH THEREOF AND A SECOND VERTICAL PORTION THE HEIGHT OF WHICH SECOND PORTION IS RELATIVELY LARGE RELATIVE TO HORIZONTAL LENGTH WHILE THE WIDTH REMAINS SUBSTANTIALLY CONSTANT WITH THE WIDTH OF SAID FIRST PORTION, THE HORIZONTAL LENGTH OF SAID SECOND PORTION BEING GREATER THAN THE WIDTH THEREOF; PLATE MEANS DISPOSED WITHIN SAID ENCLOSURE SUPPORTING ONE END OF THE HORIZONTAL SECTIONS OF THE HEAT TRANSFER MEMBERS IN SPACED RELATION TO SAID CASING MEANS, SAID PLATE MEANS HAVING OPENINGS THEREIN PROVIDING INLETS FOR SAID MEMBERS; PARTITION MEANS INCLUDING A SUBSTANTIALLY VERTICAL SECTION AND A SUBSTANTIALLY HORIZONTAL SECTION, SAID VERTICAL SECTION SUPPORTING THE OTHER END OF SAID HEAT TRANSFER MEMBERS AND PROVIDING OUTLETS FOR SAID HEAT TRANSFER MEMBERS, SAID PARTITION MEANS FORMING WITH SAID CASING MEANS AND SAID PLATE MEANS A COMPARTMENT WITHIN SAID ENCLOSURE ACCOMMODATING SAID HEAT TRANSFER MEMBERS, SAID PARTITION MEANS DEFINING AN OPENING HAVING A VERTICAL PORTION AND A HORIZONTAL PORTION; A FAN ASSEMBLY INCLUDING A FAN MEMBER AND A PARTIAL SCROLL SUPPORTED ON SAID PARTITION MEANS AND DISCHARGING THROUGH THE OPENING IN SAID PARTITION MEANS SO THAT AIR DISCHARGED FROM THE FAN IS INITIALLY DIRECTED DOWNWARDLY OVER THE FIRST SUBSTANTIALLY HORIZONTAL SECTIONS OF THE HEAT TRANSFER MEMBERS AND FORWARDLY OVER THE SECOND SUBSTANTIALLY VERTICAL SECTIONS OF THE HEAT TRANSFER MEMBERS UTILIZING THE SPACE DEFINED BY THE CASING, PLATE AND PARTITION MEANS FOR DIFFUSION TO THE OUTLET OF SAID CASING. 